Typically, an internal combustion engine with dry sump lubricating system has a feed pump which supplies lubricating oil from an oil tank disposed outside the engine body to the moving parts in the engine. Oil which has dropped down into a crankcase after circulating through the engine is immediately picked up from the crankcase and sent back into the oil tank by means of a return pump. To ensure that the crankcase does not fill with oil, the pumping capacity of the return pump is greater than that of the feed pump. Unfortunately, this means that a quantity of air and other gases is returned to the oil tank together with the returned oil.
FR2028926 describes an oil tank in which a centrifugal de-aerator is housed in the top of the oil tank in order to release the air from the oil before being returned from the bottom of the tank to the engine. The centrifugal de-aerator comprises a non-rotating tube which has a tangentially extending oil inlet whereby the air and oil mixture, which is extracted from the engine by the return pump, flows in a rotating motion around the interior surface of the tube. Hence, the oil flows into the lower region of the tank whereas the air can escape from the tube by an opening located in the top of the tube and then from the oil tank by means of an air outlet.
It is a disadvantage of such an oil tank that when the air leaves the centrifugal de-aerator there is opportunity for condensation to form due to the temperature difference between the interior surface of the centrifugal de-aerator and the interior surface of the tank. The condensate settles inside the tank at the cooler internal walls of the tank and falls to the lower region of the tank. This condensation causes degradation of the oil by reducing its rust protection abilities and its resistance to aging and thus creates oxidation problem in the engine.
The inventors herein have developed an improved oil tank which overcomes or minimises the above disadvantages.
According to the invention there is provided an oil tank for a dry sump engine, the oil tank having a housing having an upper region and a lower region in which the oil is contained, the lower region having an oil outlet and the upper region having an air outlet and housing a swirl tube connected to an oil inlet for air to separate from the incoming oil, wherein the oil tank has in its upper region a condensation trap which is arranged to reduced flow of droplets of condensation from the upper region into the lower region.
Preferably, the condensation trap is arranged to conduct droplets of condensation into contact with the swirl tube to promote vaporisation of the condensation collected.
Conveniently, the condensation trap comprises at least one baffle plate shaped to form a collector area which slopes towards the swirl tube. Each baffle plate may be secured to the swirl tube and the upper region of the tank.
Also preferably, each overflow comprises several apertures.
Preferably, the condensation trap comprises two substantially dished baffle plates spaced apart from each other and arranged in the upper region.
The above advantages and other advantages, and features of the present invention will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings, and from the claims.